Grand Theft Auto V – Do GTA 5 Saves Back-Up to a Cloud Service?

There are synchronization services which can make specific folder(s) identical across multiple machines - that sounds like it could satisfy all your needs except for the 3rd party tools, which I'm not entirely sure what you want for - and it seems you're not so sure either, as you're asking for recommendations.

For example, you could set it up so that

C:\whatever\my fav game\save data on computer A is always identical in content to

D:\something\save data on computer B.

A service I can recommend in that regard is Syncplicity - a few GB free and it allows you to synchronize whatever folders you want, unlike services such as Dropbox which dictate which folder to use. I mean dropbox might be great for other uses, but if you want to just synchronize the folder the game already uses for saves, it's not as convenient.

Well, hopefully you'll find a better answer, but one workaround is to simply back up some of your older saves to another directory.

On Windows 7, my saves are stored in

C:\Users\MyUserName\Documents\BioWare\Mass Effect 2\Save\John_12_Soldier_260110

That last bit differs on a character-by-character basis. You could grab the .pcsav files from there and move them to a backup directory. Now you've got some archived saves and free slots. If you want to restore them later, you just drop them back in (though you probably need to make sure you aren't bringing the total over 50 if you do).